As well known, all kinds of cooking vessels are used to cook food in many places like houses, restaurants and so on. While the cooking vessel such as a pot, frying pan, etc. is being used, however, food frequently sticks to the bottom surface of the cooking vessel to cause the cooking state to be not clean, and further, due to the chemical features of various seasoning added upon cooking, harmful chemical reactants may be produced to cause the erosion of the cooking vessel.
So as to solve the above-mentioned problems, accordingly, there have been proposed a variety of products each having a film layer formed on the bottom surface thereof to provide a non-stick function. At this time, the non-stick function can be obtained by applying the film layer made of a coating material such as Teflon or ceramic to the surface of the cooking vessel to prevent food from sticking to the surface of the cooking vessel.
One example of conventional cooking vessels having the non-stick function is disclosed in Korean Utility Model Publication No. 20-1994-0003569 (hereinafter referred simply to as ‘patent document 1’), wherein a ceramic layer and a Teflon layer are sequentially coated on the inner bottom surface of the cooking vessel, thereby increasing the separation of the surface of the cooking vessel from food during cooking, improving erosion resistance, and keeping good bonding state of the Teflon layer.
According to the patent document 1, however, the ceramic layer and the Teflon layer are laminated just on the inner surface of the raw material, so that if an external impact or a given temperature is applied to them, they may be easily peeled off and damaged. That is, the non-stick effect disappears at the portion of the film layer on which the ceramic layer and the Teflon layer are damaged, and further, the damaged film layer is mixed with the food during cooking to give a negative effect to the human body.
So as to solve the problems generated in the patent document 1, on the other hand, there has been suggested Korean Patent No. 10-0804387 (hereinafter referred simply to as ‘patent document 2’), wherein a plurality of concave and convex portions is formed on the bottom surface of the cooking vessel and a coating layer is formed on the concave portions so as to prevent food from sticking to the bottom surface of the cooking vessel.
However, the patent document 2 has the following problems.
Firstly, the formation of the plurality of concave and convex portions on the bottom surface of the cooking vessel is conducted by means of silk screen printing, so that ink smearing seriously occurs according to the degree of the concentration or temperature of ink, thereby failing to achieve the concave and convex portions having uniform heights.
Secondly, so as to form the concave and convex portions on the bottom surface of the cooking vessel, a stainless steel plate is fixed below a silk screen film on which holes are formed, while having a given space from the silk screen film, and next, ink is applied to the silk screen film and pushed to the holes of the silk screen film by means of rubber or brush, thereby conducting printing on the stainless steel plate, so that ink smearing may occur in accordance with the degree of skill of a worker, the whole printing work may be unstably conducted, and when relatively large area is printed, constant printing quality cannot be maintained on the starting and finishing portions of the area.
Thirdly, relatively large working space is needed, it is hard to conduct precise work, and specifically, a number of defective products are made.
Fourthly, a beehive (hexagonal) pattern is formed on the bottom surface of the cooking vessel, and in this case, the beehive pattern is formed by a solid line, so that if the width of the solid line is 0.5 mm and the length of one surface of the hexagon is 5 mm, the non-stick effect can be obtained through the width of the solid line but can be lost in the lengthwise direction of the solid line, thereby causing food to stick to the bottom surface of the cooking vessel.
Lastly, when oil pours on the bottom surface of the cooking vessel, it gathers inside the hexagon, so that the oil is not distributed evenly to cause food to stick to the bottom surface of the cooking vessel, thereby making it hard to cook.